Former NSA contractor Edward Snowden obtained access to classified documents by stealing one of his co-worker's passwords, according to an unclassified NSA memo obtained by NBC News.

That co-worker resigned after being stripped of his security clearance, according to the report, which also indicated that a member of the US military and a contractor were barred from accessing National Security Agency facilities after being linked to actions that may have aided Snowden. Their status is currently under review, according to the memo (PDF).

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The civilian NSA employee entered his password into Snowden's computer "at Snowden's request," according to a February 10 memo sent to key members of Congress. "Unbeknownst to the civilian, Mr. Snowden was able to capture the password, allowing him even greater access to classified information," according to the memo, which was signed by Ethan Bauman, the NSA's director of legislative affairs.

Although the civilian employee was unaware that Snowden "intended to unlawfully disclose classified information," the memo states that the employee's security clearance was revoked in November after it was determined he "failed to comply with security obligations." The memo was sent to congressional intelligence and judiciary committees after senior members of Congress demanded to know whether the NSA was disciplining any of its employees in connection with the leak of sensitive documents.